Landslides: Types, Mechanisms and Modeling (Book Chapter)
Kalenchuk, K.S., Hutchinson, D.J., Diederichs, M.S., and Moore, D. 2012. Downie Slide, British Columbia, Canada. Landslides: Types, Mechanisms and Modeling, (eds. J.J. Clague and D. Stead), Cambridge University Press: 345-358.
The Downie Slide case history demonstrates the importance of detailed site investigation and long-term monitoring, as well as the need for reinterpretation of the local geologic, structural, and groundwater conditions, and reassessment of slope stability as new information becomes available. Forty-five years of investigation, monitoring, and assessment have been carried out at Downie Slide. The long history of studies, coupled with recent technological advances in analytical tools, has enabled us to better understand the behavior of large complex landslides.
Downie Slide, the largest known active slope instability in the world, is located 64 km north of the Revelstoke Dam on the west bank of the Revelstoke Reservoir, in the Columbia River valley, British Columbia, Canada (Fig. 28.1). This massive, active, composite, extremely slow-moving rockslide has a volume of 1.5 billion m3. It measures 3300 m from toe to head scarp and 2400 m along the toe, with a maximum thickness of approximately 250 m. Downie Slide is thought to have been initiated by glacial retreat, approximately 10,000–12,000 years ago (Piteau et al., 1978 ; Brown and Psutka, 1980). Total slope displacements are estimated between 250 and 300 m (Patton and Hodge, 1975), but there is no evidence that the slide failed rapidly or blocked the valley (BC Hydro, 2010).